1. Field of the Invention
This invention relates to combustion chamber liners for use in apparatus such as a gas turbine engine, and more particularly, to a combustion chamber liner having an emergency cooling and detection system activated by a failure in the combustion chamber liner.
2. Description of the Prior Art
A cross-reference is made to U.S. patent application Ser. No. 07/082,861, filed on Aug. 6, 1987, entitled "Internally Cooled Combustion Chamber Liner" by the same applicant as herein.
Combustion apparatus or combustors are used in various applications to produce heat or burn a fuel in a controlled environment. One particular use of combustors has been in the area of gas turbine engines. As employed in a gas turbine engine, a combustor ordinarily includes an exterior housing and an interior combustion chamber. Fuel is combusted in the interior of the combustion chamber producing a hot gas usually at an intensely high temperature such as 3,000.degree. F. or even higher. To prevent this intense heat from damaging the combustor before it exits to a turbine, a heat shield or combustion chamber liner is provided in the interior of the combustion chamber. This heat shield or combustion chamber liner thus prevents the intense combustion heat from damaging the combustor or surrounding engine.
In the past, various types of combustion chamber liners have been suggested and used. In addition, a variety of different methods have been suggested how to cool these liners so as to withstand greater combustion heat or prolong the useable life expectancy of the liner. U.S. Pat. No. 2,548,485 by Lubbock and U.S. Pat. No. 3,918,255 by Holden disclose various types of combustion chamber liners. Other U.S. Patents that describe cooling of combustion chamber liners include U.S. Pat. Nos. 4,004,056 by Carroll, 4,269,032 by Meginnis et al, 4,302,940 by Meginnis, and 4,315,406 by Bhanger et al. U.S. Pat. No. 4,064,300 by Bhanger has also described a two sheet laminate being connected by heat conductive portions with a cooling fluid passing between the two sheets.
Also in the past, combustion chamber lines were made of special metal alloys. These metal alloys were manufactured to withstand the intense heat in the combustor and allow for a controlled heat transfer so as not to damage or endanger the surrounding engine. However, the cost of these types of metal alloys was unreasonably high and thus lead to the use of a metal and ceramic combination as materials for liners. The use of a metal and ceramic combination greatly reduced manufacturing cost of liners in addition to providing a more efficient heat shield.
A problem arises in using presently available combustion chamber liners that have a combination ceramic and metallic material in that ceramic material is normally brittle whereas metallic material is normally ductile, as a result, thermal gradients or differing thermal expansions between the ceramic and metallic material from the intense heat of the combustion chamber results in a substantial likelihood of a crack or break in the ceramic material. This crack or break in the ceramic material is generally known as a failure and allows heat to escape the combustion chamber resulting in further damage to the combustion chamber liner, the combustor and possibly the entire engine.
A further problem arises in using presently available combustion chamber liners having metal and ceramic layers in that in the event that a failure occurs in the ceramic material there are no means available to supply sufficient coolant to provide a directed cooling of the area about the failure to prevent further failure or damage caused by the heat in the combustion chamber.
A further problem arises in that ceramic and metallic combination combustion chamber liners do not have a suitable means to compensate for the inherently different thermal expansion properties of the materials in addition to providing a means for cooling the interior of a combustion chamber liner and providing an emergency cooling for areas where failure has occurred.
A further problem arises in that in the event that a failure does occur, the combustion chamber and combustor are ordinarily contained in an apparatus. such as a gas turbine engine, and detection of the failure will only be discovered during internal manual inspection when the combustor is not operating or by a catastrophic failure perhaps resulting in the loss of human life.